Generally, it has long been a practice to dispense liquid mercury into a lamp after the lamp has been exhausted and hermetically sealed. In order to efficiently and safely effect such mercury dispersion, numerous techniques have been employed. For example, liquid mercury has been introduced into a lamp by way of the exhaust tubualtion of the lamp. However, such techniques have frequently been considered both hazardous and expensive.
Other methods for effecting liquid mercury release in an evacuated envelope include the containment of the liquid mercury in a glass or metal container with a wire wrapped about the glass container. Thereafter, heat preferably in the form of RF energy, is utilized to effect a rupturing of the container and dispersement of the liquid mercury.
Another approach to the dispensing of a liquid mercury in an arc lamp is set forth in a co-pending application U.S. Ser. No. 374,605, entitled "Method of Dispensing Mercury Into A Fluorescent Lamp And Lamp To Operate With Method," filed in the names of the inventor of the present application and Ralph P. Parkes, Jr., and assigned to the Assignee of the present application. Therein a mercury dispensing target is located within an exhausted lamp having a coil at each end of the lamp. The dispensing target is affixed to one lead of one of the coils and positioned intermediate the coils disposed at opposite ends of the lamp. A direct current is passed through the lamp and the dispensing target functions as the anode and collects the discharge current in an amount sufficient to heat the target and dispense the mercury therein.
Although the above-described technique has been and still is suitable for use in a variety of structures, it has been found that there are lamps and structures available wherein special conditions are desirable. More specifically, a lamp having a coil at one end connected to a DC potential source and a coil with a pair of electrical leads having a mercury dispensing target connected to one of the electrical leads at the opposite end of the lamp requires that the electrical lead having the target thereon be connected to the potential source. In this manner, the mercury dispensing target collects and is heated by a high proportion of the electric current. It can readily be seen that a lamp having a pair of electrical leads with the mercury dispensing target on one of the leads could be connected to the potential source in a manner such that the lead with the target thereon is not the one connected to the potential source. Thus, the dispenser target would fail to collect a high proportion of the electron current, fail to heat and fail to dispense the liquid mercury.